php - Unable to Receive PayPal IPN Response in Code Igniter

Solution:

I found the solution! I wrote the IPN handler inside a controller that allows access to users who are logged in as admin. Apparently, the IPN method was denying access to PayPal to verify the transaction. I figured this out and wrote the IPN method in a different controller and everything worked perfectly.

I also changed my IPN handler to this code (although the original might still work... i didn't try it):

class Paypal_ipn extends MY_Controller {
    public function __construct() {
        parent::__construct();
        $this->load->model('product_model');
        $this->sandbox = $this->config->item('sandbox'); 
        $this->paypal_host = $this->config->item('paypal_host'); 
        $this->paypal_url = $this->config->item('paypal_url'); 
        $this->business_email = $this->config->item('business');
    }


    public function ipn() {
        // STEP 1: Read POST data

        // reading posted data from directly from $_POST causes serialization 
        // issues with array data in POST
        // reading raw POST data from input stream instead. 
        $raw_post_data = file_get_contents('php://input');
        $raw_post_array = explode('&', $raw_post_data);
        $myPost = array();
        foreach ($raw_post_array as $keyval) {
          $keyval = explode ('=', $keyval);
          if (count($keyval) == 2)
             $myPost[$keyval[0]] = urldecode($keyval[1]);
        }
        // read the post from PayPal system and add 'cmd'
        $req = 'cmd=_notify-validate';
        if(function_exists('get_magic_quotes_gpc')) {
           $get_magic_quotes_exists = true;
        } 
        foreach ($myPost as $key => $value) {        
           if($get_magic_quotes_exists == true && get_magic_quotes_gpc() == 1) { 
                $value = urlencode(stripslashes($value)); 
           } else {
                $value = urlencode($value);
           }
           $req .= "&$key=$value";
        }

        // STEP 2: Post IPN data back to paypal to validate

        $ch = curl_init($this->paypal_url);

        $headers = array(
            'POST /cgi-bin/webscr HTTP/1.1',
            'Host: ' . $this->paypal_host,
            'Content-Type: application/x-www-form-urlencoded; charset=utf-8',
            'Content-Length: ' . strlen($req),
            'User-Agent: PayPal-IPN-VerificationScript',
            'Connection: Close'
        );

        curl_setopt($ch, CURLOPT_HTTP_VERSION, CURL_HTTP_VERSION_1_1);
        curl_setopt($ch, CURLOPT_POST, 1);
        curl_setopt($ch, CURLOPT_RETURNTRANSFER,1);
        curl_setopt($ch, CURLOPT_POSTFIELDS, $req);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 1);
        curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 2);
        curl_setopt($ch, CURLOPT_FORBID_REUSE, 1);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

        if( !($res = curl_exec($ch)) ) {
            curl_close($ch);
            exit;
        }
        curl_close($ch);

        // STEP 3: Inspect IPN validation result and act accordingly

        if (strcmp ($res, "VERIFIED") == 0) {
            // check whether the payment_status is Completed
            // check that txn_id has not been previously processed
            // check that receiver_email is your Primary PayPal email
            // check that payment_amount/payment_currency are correct
            // process payment

            // assign posted variables to local variables
            $item_name = $_POST['item_name'];
            $item_number = $_POST['item_number'];
            $payment_status = $_POST['payment_status'];
            $payment_amount = $_POST['mc_gross'];
            $payment_currency = $_POST['mc_currency'];
            $txn_id = $_POST['txn_id'];
            $receiver_email = urldecode($_POST['receiver_email']); 
            $payer_email = $_POST['payer_email'];
            $school_id = $_POST['custom'];

            // further checks
            if($payment_status == 'Completed') {

                $message = 'IPN verified successfully!';
                $this->email_developer($message);

                // Insert the transaction data in the database
                $this->product_model->insert_transaction_details($_POST);

            } else {

                $message = 'Payment could not be verified!';
                $this->email_developer($message);  

            }

        } else if (strcmp ($res, "INVALID") == 0) {
            // log for manual investigation
            $message = 'IPN Invalid!';
            $this->email_developer($message);

        }
    }

}
Copy code

For those that might experience my predicament, ensure you also do the following:

1. If you enabled Cross Site Request Forgery (CSRF), ensure the IPN listener/handler is whitelisted, else IPN message will fail (Error 403 in PayPal IPN history).
2. To be sure your IPN listener is working well, run it as a URL and see the response. If there is any error, it won't work. For response, trying echoing "Verified" or "Invalid".
3. Use the PayPal IPN Simulator to test the process. Include a procedure that will submit information to the database upon success.

I hope it helps someone.

Solution:

use php://input instead of $_POST

reson described here in details : PHP "php://input" vs $_POST

also paypal has documentation for implementing IPN Listener and its in php as well Paypal tutorial